Almost a third of people who voted Tory in 2010 will switch allegiance to UKIP in the European elections in 2014, a new poll indicates.

Research from YouGov shows 32% of those who backed David Cameron at the last General Election would desert him if next year's vote was held now.

The poll also suggests that 13% of people who voted Lib Dem in 2010 would back UKIP instead, in a further sign of the anti-Europe party's rising fortunes.

Current voting intentions for the European Parliament elections put Labour on 38%, the Tories on 27%, UKIP on 17% and the Lib Dems on 12%.

UKIP polls around 20% in most British regions but in Scotland the party has just 8% support, according to YouGov.

More men than women support the party, the findings suggest.

They also reveal that a quarter of the over-60s support UKIP, compared to 17% of 40-59-year-olds and 8% of under-40s.

David Cameron is facing a growing challenge from Ukip

Joe Twyman, YouGov’s director of political and social research, said: "With a third of Conservative supporters in 2010 already saying they will vote for UKIP in 2014, the increased focus Europe and therefore UKIP will receive in the run-up to next year's European elections means it is possible that the numbers will get worse for the Conservatives as we get closer to polling day.

"If this trend continues, it is likely UKIP will be picking up the most votes at the European elections."

The findings are further evidence that both the Tories and Lib Dems are losing support to Nigel Farage's party.

Euroscepticism has grown in Britain because of the eurozone crisis, helping UKIP to unprecedented levels in the polls.

They have also benefited from a slump in Lib Dem support since they entered coalition and disaffection with the Tories.

Mr Cameron is hoping he can stem the tide with a key speech on Europe on Friday in which he will set out his plans for Britain.

He is expected to say he will pursue a fresh settlement with Brussels before putting that to the British people after the next election.

The Prime Minister has called an in-out referendum a "false choice" and insists it is better for the UK to remain in the EU.